It’s fascinating that thoughts – from the brain- are actually tangible using different tools in neuroscience. Moreover, such “ thoughts” could be manipulated in various ways to eventually interfere with behaviors. Although the brain is neither light active nor light sensitive intrinsically, novel technologies have been developed recently to enable both optical recording and optical activation/inhibition of neural activities. In this talk, I will first describe my precious work on optical recording of spiking activities (the neural “code”) from cultured hippocampal neurons using gold plasmonic nanoparticles, which is the first time to use gold nanoparticles to look at neural spikes to the best of our knowledge. The neural signals are detected through the transient change in the scattered light from active hippocampal neurons grown on gold nanoparticle arrays. The second part of the talk is about my other previous work on direct optical stimulation and inhibition of neural activities from genetically targeted neurons which express Channelrhodopsin (ChR2), a light sensitive cation channel. A tapered optical fiber construct has been developed to deliver local stimulation light and record neural activities simultaneously. Transient group activities are triggered in ChR2 mice brain slices, which can essentially be treated as traveling pulses in a neural network using neural equivalence of mean field theory. Finally, I will talk about my current work of using ChR2 to study the development of visual maps.